Abstract: Three short-term rheological measurements on some model personal care emulsions showed good correlation with long-term physical instability of the emulsions. Use of these rheological measurements can shorten the time to test the stability of new formulations.

Emulsions used in personal care and cosmetic formulations--both oil-in-water (O/W) and water-in-oil (W/O) types--need to satisfy a number of criteria. They must demonstrate physical stability over 2-3 years under various conditions, such as temperature variation and stress induced by vibration during transportation. They must also maintian the proper consistency (rheology) to achieve good skin-feel, spreading and delivery of actives. Finally, the safety of the ingredient used must be assured to avoid any skin irritation or adverse effects on contact with the skin.